The sole focus of the Windows Insiders - who include employees from Microsoft, hardware manufacturers and software developers - is release quality.
Having the Insiders test new releases is far superior to having only Microsoft employees do the testing. Microsoft can't possibly test a release candidate on every combination of hardware and software, and Microsoft doesn't have the proprietary knowledge of third-party hardware and software products needed for a full evaluation.
Sorry, but I have never seen a more inaccurate post for any Microsoft operating system release since I have been using computers. Windows 10 is the all-time worst quality in a Microsoft release of any product I have ever seen. It is worse than Windows 3.1, and that is pretty bad.
These Insiders are really doing a poor job of ensuring quality. That is for sure.